In the agricultural chemical industry, triazoles are an important class of fungicides. One such fungicidal triazole is 2-[2-(1-chlorocyclopropyl)-3-(2-chlorophen-yl)-2-hydroxypropyl]-2,4-dihydro-[1,2,4]-triazole-3-thione, also known as prothioconazole. Numerous prothioconazole-based products have been introduced by Bayer CropScience into the market since 2004 under brands such as Proceed®, Proline®, Input® and Prosaro®. The preparation of a number of agricultural microbiocides such as prothioconazole, prepared from triazolyl derivatives, is disclosed in U.S. Pat. No. 5,789,430.
Unfortunately, prothioconazole is subject to chemical degradation, and aqueous dispersions of prothioconazole, in particular, microdispersions, may become chemically unstable, particularly when formulated at low, ready-to-use concentrations, significantly reducing their shelf life. Losses of ten to fifteen percent by weight of the active ingredient over time have been observed in low concentration formulations. In formulations of agricultural chemicals having one or more active ingredients (ai's) that are present at a nominal declaration (label declaration) of greater than 1 percent by weight (1%) but less than 20 percent by weight (20%), current government regulations require that active ingredients be present in amounts that deviate no more than 5 percent by weight from the labeled concentration.]] If the nominal declaration is <1%, the upper and lower certified limits (range) defaults to ±10%; if the nominal declaration is >20% then the upper and lower certified limits (range) defaults to ±3%
It would be desirable to develop chemically stable aqueous dispersions of prothioconazole and processes for preparing them so as not to deviate beyond the certified limit range(s) as established by way of the nominal label declaration.